ANNALS OF GEOPHYSICS, 53, 5-6, 2010; doi: 10.4401/ag-4872

The ash-fall hazard from a Plinian eruption at Colima Volcano, Rita Fonseca1,*and Ana Lillian Martin Del Pozzo1

1 Instituto de Geofisica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacan Mexico D.F., Mexico

Article history Received November 15, 2010; accepted November 23, 2010. Subject classification: Volcanology, Volcanic risk, Ash-fall hazard, Colima Volcano, Mexico.

ABSTRACT flows that destroyed farms, and caused roof collapses, forest fires, loss of livestock and crops, contamination of water The historical eruptive activity at Colima Volcano has been characterized resources, and morphological changes to the ravines and by Strombolian and Merapi type eruptions and Vulcanian explosions crater [Waitz 1932, Lugo et al. 1993, Martin Del Pozzo et al. associated with dome growth, which have ended in a Plinian eruption 1995a, Saucedo 1997]. The last of these eruptions was about every 100 years. The situation now prevailing at Colima Volcano is characterized by an eruptive column over 23 km high, and it similar to that which preceded these explosive eruptions, when a dome fills occurred in 1913, causing darkness in Ciudad Guzmán, the crater. This study proposes seven scenarios for the ash-fall from a Sayula and , which are located between 26 km Plinian eruption, based on historical eruptive activity, isopach thickness and 140 km from CV [Arreola 1915, Saucedo et al. 2010]. The from the 1913 Plinian eruption, land use, socioeconomic data, and a 15- area covered by the ash at that time is now populated by year statistical wind study realized with daily radiosonde data grouped more than 5 million people. according to four altitudinal levels: 4,000-9,000 (I); 9,000-14,000 (II); The present-day activity at CV is associated with 14,000-17,000 (III) and 17,000-28,000 (IV) m a.s.l., based on common wind dome growth and destruction of the crater, which has speeds and directions. We have integrated the wind distribution at level IV become more explosive after several decades of lava and estimated the ash dispersion for a Plinian eruption. From January to emission. These Vulcanian eruptions are similar to those March, the main impact would be towards the northeast, in April and in that preceded the Plinian eruptions, suggesting the October, towards the east, in May, towards the north-northeast or north- possibility of a Plinian phase in the near future, like those northwest, from June to August, towards the northwest, in September, that occurred in 1818 and 1913. In this study, we identify towards the west, and in November and December, towards the west- and evaluate the areas that will be vulnerable to ash-fall in southwest. The fallout would damage the coniferous forests of the Colima Plinian eruption scenarios, based on analyses of historical National Park, two lagoons and three lakes. More than 30 million people eruptive activity, isopach thickness from the 1913 eruption, living in Guadalajara, Mexico City, Leon and Colima would suffer eye, a vertical wind study, and socioeconomic characteristics of respiratory and skin problems. The proximal areas, such as Ciudad the cities involved. Ash-fall would form secondary lahars Guzman, would be subject to roof collapsing and communication by obstructing the steep ravines on CV, especially during problems. The agricultural and livestock sectors would suffer severe the summer. Furthermore, the steep upper slope of the CV financial losses. The Queseria sugar mill, the Atenquique paper mill, and cone and its growth on the older Nevado de Colima and the cement plants in Zapotiltic would halt work due to chimney obstruction collapsed CV, represent unstable conditions for its southern and machinery abrasion. Four thermoelectric plants, twenty airports and flank [Lugo et al. 1993, Martin Del Pozzo et al. 1995a, four commercial ports would be affected if the eruption occurs in summer. Cortes et al. 2005].

1. Introduction 2. Methodology Colima Volcano (CV; 19˚30´44˝ N; 103˚37´02˝ W) is A detailed revision of historical and current documents located in the western part of the Trans-Mexican Volcanic regarding the volcanic activity of CV was carried out to Belt at nearly 4,000 m above sea level (a.s.l.), and it is one of evaluate its eruptive behaviour. Field work allowed us to the most active volcanoes in Mexico (Figure 1). According to identify the explosive deposits of the 1818 and 1913 eruptions detailed historical analysis and field work, Plinian eruptions and their distribution. of CV have occurred on the order of once every 100 years. Considering the possibility of a new explosive event, a These have had significant impact on the surrounding areas wind study was carried out, based on the 15-year radiosonde because of widespread fall deposits, surges and pyroclastic database (1990-2005) from the Manzanillo station of the

51 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Figure 1. A: Map of the Colima Volcano and cities affected in 1913 by ash fall. Lu: La Lumbre; SAnt: San Antonio; Mu: El Muerto; Du: Durazno; Cdn: Cordoban. B: Localitation of Volcano in Mexico.

National Meteorological Service (19˚07´ N, 103˚33´ W), and consistent with the regional atmospheric circulation model complemented with data from the Guadalajara station [Fonseca et al. in preparation]. (20˚39´57˝ N, 103˚22´48˝ W). The statistical analysis was Scenarios for future Plinian eruptions with a height of based on the daily radiosonde database, which has 15 23 km were prepared for each month, by integration of pressure levels and includes wind direction (degrees), wind historical and socioeconomic characteristics per city, field intensity (m/s) and altitude (m). The wind dataset was then data of ash isopach distribution of the 1913 eruption, and organized into four altitudinal levels: I, 4,000-9,000; II, 9,000- dominant monthly wind vectors at 17,000-28,000 m a.s.l. 14,000; III, 14,000-17,000; and IV, 17,000-28,000 m a.s.l. These are all plotted on 1:250,000 and 1:1,000,000 scale These were subdivided according to the variations in wind maps. The socioeconomic data (population, economic speed and direction. Levels I and II showed wind-speed activity, airport type, flights/year, roads, power stations) was variations of between 100 km/h and 150 km/h. For levels III based on the 2005 census [INEGI 2005] and the statistical and IV, the wind-speeds were 150 km/h. These data are also yearbook [INEGI 2007].

52 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

3. Population and infrastructure The CV region was the seat of pre-Colombian cultures that flourished in western Mexico, and the volcanic activity was not an obstacle for the socioeconomic development of the area. In the 1913 eruption, more than 732,426 inhabitants were affected by ash-fall, while from 1913 to 2005, the population in the same area increased to more than 5 million people (Table 1). Ash also fell on Mexico City in 1818, which now has more than 20 million inhabitants. Other cities, like Guadalajara and Leon, had ash-falls in 1770 and 1913, and they now have more than 4 million and 1.3 million inhabitants, respectively. The CV is a National Park, and it also includes agricultural land and ranches. Private environmental protection areas, such as El Borbollon, the Jabalí ranch, and the Hacienda San Antonio Hotel, are located from between 9 km and 12 km from CV. During the field work, we confirmed that the Borbollon and Jabalí ranches have sustainable management of natural resources and employ ! local people. Perception of the volcanic hazard has Table 1. Main cities affected by the 1913 eruption, and the populations in strengthened the communication between the people 1913 and 2005. working in these locations and the authorities. The permanent crops are mainly fruit, vegetables, cereals, sugar cane and agave, which have important roles in both the local and regional economies. Sugar cane is the main crop, which supplies the Queseria sugar mill that is located 15 km from CV. The El Borbollon ranch grows coffee, which is sold in the city of Colima. In San Marcos, 15 km from CV, there is a greenhouse that grows exotic flowers for export. Most of the population works in farming, trade, administration services, tourism and construction. There are a total of 14 international airports in the cities of Aguascalientes, Guadalajara, Leon, Manzanillo, Mazatlán, México City, Morelia, Puebla, , Querétaro, San Luis Potosi, Saltillo, Toluca and Zacatecas, all of which are within 725 km of CV, and are included in the area that experienced ash-fall in 1913 (Table 2). There are also six national airports in the cities of Zamora, Celaya, Colima, Tepic, Uruapan and Cuernavaca. Even with small eruptions, such as those in May 2001 and September 2005, the airport in the city of Colima was closed due to ash-fall. With larger events, the ash-fall would damage aeroplanes and power plants, and disrupt airports, causing short circuits in Table! 2. List of cities with airports and number of flights per year (2006 data). computers and burning out transformers [Guffanti et al. 2009]. Due to its abrasive nature, ash is hazardous to north of Mexico City, Salamanca, San Luis Potosí, Tepic and aeroplane electronic communication systems, turbines and Tula are important sources of income, as are the fuselage [Casadevall 1992]. petrochemical and refinery industries in Salamanca, The main roads in the area have constant traffic, such as Veracruz and Tepic. The power stations in Colima, the Federal and Panamerican highways that connect Colima, Manzanillo and Guadalajara supply more 1.5 million Guadalajara and México City with northern Mexico. The consumers with electricity, and these might be affected in the thermoelectric plants in Manzanillo, Mazatlán, Acolman, future by a Plinian eruption.

53 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Figure 2. Colima Volcano historical activity. Based on: Tello 1651, Perez de Leon 1789, Mota Padilla 1742, Bárcena 1887, Puga 1889, Vizcarra 1891, Starr and Arreola 1903, Diaz 1906, Arreola 1915, Waitz 1932, Mooser 1961, Thorpe et al. 1977, Luhr and Carmichael 1982, Medina 1983, Flores 1987, Martin Del Pozzo and Romero 1988, De la Cruz 1993, Vizcaino 1993, Martin del Pozzo et al. 1995b, García-Acosta and Suárez 1996, Saucedo 1997, Breton et al. 2002, Reyes and De la Cruz 2002, Zobin et al. 2002, Navarro et al. 2003, Smithsonian Institution [1988, 1993, 2000], University of Colima Bulletin. : Lateral activity (Volcancito 1869-1873). Dashed line: no data.

4. Eruptive history ash-fall and pyroclastic flows and coincided with the death The 430-year historical records of CV show that it is a of many young people, although these deaths might have very active volcano, with a cyclic behaviour that ends in been associated with an epidemic that broke out in the same Vulcanian and Plinian eruptions approximately every 100 year and that killed more than half of the populations of 22 years. The first eruptive analyses were carried out by Bárcena villages in Colima [Tello 1651, Perez de Leon 1789]. The [1887] and Starr and Arreola [1903], who reported that CV following eruptions in 1585, 1587, 1589, 1590, 1602, 1606 and has effusive and explosive periods between resting intervals, 1611 produced important lapilli, scoria and ash-falls, but the and that the intensity and magnitude of the eruptions had main impact of the stronger eruptions in 1576 and 1611 was increased with time. Waitz [1932] considered that CV has a on livestock and agriculture, in addition to the constant fear cyclic behaviour, and later studies by Luhr and Carmichael of the population [Tello 1651, Mota Padilla 1742, Bárcena [1982], Martin Del Pozzo and Romero [1988] and Robin et al. 1887, Ciudad del Real 1976, Breton et al. 2002]. [1991] have also confirmed eruption cycles in the recent activity of CV. These studies have proposed four historic Cycle II (1611-1690) cycles, each of which began with slow lava ascent, continued Another eruption in 1623 was attributed to CV, but intermittently with lava or pyroclastic eruptions, and ended information regarding this event is limited, and therefore the in explosive eruptions with pyroclastic flows and extensive characteristics of the eruption are not known [Tello 1651, ash-fall, which clears the crater for a new cycle. Luhr and Vizcarra 1891]. It was not until 1690 that another explosive Carmichael [1990] associated compositional variations with eruption was reported, of a Pelean type, with strong seismic the cycles, which have mostly involved basic andesitic activity [Medina 1983]. Martin Del Pozzo and Romero [1988] magmas in the second and third cycles (1690-1818, 1818-1913), considered this as the end of the second cycle. which ended in explosive eruptions. Luhr and Carmichael [1990] also considered that the 1913 eruption had more Cycle III (1690-1818) hydrous andesitic magma than that in 1818 (basic andesitic CV produced ash in 1744, 1749 and 1750, which fell on magma), because of the presence of hornblende. the city of Colima [Barcena 1887, Arreola 1915]. In 1769, lava We present here the results of a new historical analysis. flows were reported, and in 1770 there was an explosion that Each cycle ends in a VEI 4 Plinian eruption (Figure 2). For was preceded by tremors and loud noises, and which formed decades, lava ascends until it reaches the crater and a dome a dense ash column and pyroclastic flows. Ash fell on is formed. Afterwards, Merapi flows and hot avalanche Guadalajara for 3 days, and the pyroclastic flows filled the La deposits are generated by lava flow gravitational collapse, or Joya ravine on the southwest, covering plants, cattle, birds from dome growth on a steep slope. The Vulcanian and other animals [Perez de Leon 1789]. The ash-fall resulted eruptions grow stronger and more frequent, producing ash- in darkness in the surrounding areas, which reached the city fall and pyroclastic flows, and a new Plinian eruption of Durango, 550 km north of CV [Perez de Leon 1789]. Due eventually expels the dome, producing ash-fall up to to the extent of the ash-fall and the 3-hour duration of the distances of more than 700 km from CV, and forming block eruption, it appears to have been a VEI 3 event. CV and ash flows up to 15 km away [Saucedo et al. 2010]. continued to be active in 1771, 1780 and 1794-1795. Lava flows, rockslides, ash emission, and fumarolic activity were Cycle I (?-1611) recorded in 1804, 1806 to 1809, and 1811 [Barcena 1887, Early records refer to eruptions with tephra and Arreola 1915]. pyroclastic flows (Figure 2). An eruption in 1576 involved At the beginning of 1818, the crater was filled by a

54 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO dome, and on February 15, 1818, it was destroyed by an northeast as far as 725 km from CV [Waitz 1932]. The 10-15- eruption that started with an explosion that was heard in the cm-thick ash and pumice fall in Ciudad Guzman caused roof cities of Ciudad Guzman and Leon, 26 km and 275 km from collapses, and 0.5 cm of ash fell on Guadalajara, and 0.01cm CV, respectively [Waitz 1932]. The tephra cloud «covered the on Zacatecas, Aguascalientes and Saltillo [Waitz 1932]. The moon» and produced darkness [Arreola 1915, Waitz 1932]; a 1913 eruption left a 400-m-diameter crater with irregular loud noise was heard two hours later (22:00 hours). The peaks on the edges [Waitz 1932]. pyroclastic flows coming down the Muerto ravine on the During the 1913 eruption, the main direction of the ash southern side of the volcano were seen by the inhabitants of plume was to the north-northeast, although people in the San Marcos. These flows destroyed the forests and killed city of Colima 30 km to the south also mentioned darkness cattle, while lapilli and ash fell to the east-northeast, mostly and that their candles blew out due to the ash in the air between 20:00 and 22:00 hours [Arreola 1915, Waitz 1932]. [Navarro, personal communication]. The ash caused damage to the roofs of the houses in Ciudad Guzman, and some collapsed because of the weight. Distal Cycle V (1913-?) ash arrived as far as Guadalajara (140 km), Leon (275 km), Lava was observed at a depth of 50 m in the crater in Guanajuato (310 km), Zacatecas (384 km), San Luis Potosi 1922, while in 1940, it had ascended nearly to summit level (425 km), Querétaro (345 km) and Mexico City (470 km). [Waitz 1932, Mooser 1961]. In 1957, loud noises were This 1818 eruption, which left an irregular funnel-shaped heard, followed by steam emission, which scared the local crater, was short and was followed by steam emissions and population. After 1958, the dome grew by 70 m in one year some earthquakes in later years [Vizcarra 1891, Waitz 1932]. [Mooser 1961, Vizcaino 1993]. Between 1961-1962 andesitic lava flows from the dome advanced 20 cm/d, reaching 1 km Cycle IV (1818-1913) to the north, northeast and northwest of the crater Lava ascended from a depth of 300 m to 200 m between [Mooser 1961]. In 1970, noises and local seismicity preceded 1834 and 1866, and in 1869, a lateral dome known as small ash emissions [Vizcaino 1993]. Between 1975 and "Volcancito" was formed on the upper north-eastern side of 1976, the volcano produced local ash-fall, two lava flows the volcano, activity that continued until 1873 [Barcena >3.5 km long and 50 m thick, and block and ash flows 4.5 1887]. In 1869, a tremor was felt in San Marcos and San km long that caused fires on the south-eastern part of CV Gabriel, which preceded lava flows, ballistics and ash [Thorpe et al. 1977]. emission, and which scared the population [Arreola 1915]. During 1981, there was fumarolic activity and ash-fall in Fumarolic activity with sporadic ash emission and the summit area, and in early 1982, lava flowed 1 km south- underground noises were reported from the central crater westward. In 1986, an ash cloud was seen from the city of in 1869, 1872 to 1874, 1877 and 1879 [Bàrcena 1887, Arreola Colima, and in 1987, an explosion produced a pit of 100 m to 1915, García-Acosta and Suárez 1996]. 150 m in diameter and 30 m to 40 m deep on the upper At the end of 1880, a central dome overflowed the crater eastern flank of CV [Flores 1987]. In 1988, fumarolic activity edge, which produced several lava flows, as well as ash alternated with small explosions. emission, in 1880-1881, 1885-1886, and 1889-1890 [Arreola After increasing fumarolic and seismic activity and 1915, Waitz 1932]. The crater was then filled again by a rockslides from the dome in 1991, a small new dome grew summit dome, but explosions in 1903 and 1908 produced pits through the summit dome. Its growth caused partial collapse in this [Starr and Arreola 1903, Diaz 1906, Waitz 1932]. of the summit dome to the south, which produced The 1913 eruption began with loud noises and thunder, pyroclastic flows and was followed by lava advance between January 17 and 18, forcing the people 7 km to the [Rodríguez-Elizarrarása et al. 1991, Gonzalez et al. 1993]. east of the volcano to abandon their farms on the higher This dome was destroyed by an explosion in 1994, which parts of CV and to take refuge on the plateau, which is today produced a crater 135 m in diameter and 40 m deep [Reyes Juan Barragan [Waitz 1932]. On January 18, ash-fall and and De la Cruz 2002]. The eruption also produced ash-fall 15 constant noise were reported; the 1880 dome was totally km to the west, impact craters up to 2 km from the crater, destroyed on January 20. At dawn on January 20, a series of and pyroclastic flows over 4 km long [Saucedo 1997]. explosions formed dense ash columns that were During 1997, the seismic crises and rockslides from the accompanied by loud noise, which lasted from 15:00 to 16:00 dome decreased after explosions [Martin Del Pozzo et al. hours. After 16:00 hours, surges and block and ash flows 2002], but in November 1998, the seismicity and rockslides descended ~15 km from the crater, which filled the ravines increased, which ended with lava extrusion from the dome. by up to 40 m [Waitz 1932]. The flows caused fires and killed On November 18, 1998, growth of a new dome and an cattle. These flows were remobilized as hot lahars during the increase in seismicity caused the authorities to evacuate the rainy season several months later, killing eight people and a population of La Yerbabuena and Juan Barragan, 10 km and lot of cattle [Waitz 1932, Saucedo 1997]. Ash fell to the north- 7 km from the crater. On November 21, 1998, new lava flow

55 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO was accompanied by Merapi flows; lava continued flowing Guzmán, and ballistics [Smithsonian Institution 2003]. In until the end of November, when collapse of the lava front September 2004, a dome started growing, which produced formed block and ash flows that reached 4.8 km in the 2-km-long block and ash flows, followed by lava flows to the Cordoban ravine [Navarro et al. 2002, Saucedo et al. 2002]. north and west-northwest that reached 1.8 km and 0.6 km in In February 1999, the seismicity increased, and it ended October 2004 [http://www.ucol.mx]. During 2005, eight with an explosion that destroyed part of the new dome. The pyroclastic flows with ash plumes from 2 km to 8.5 km noise was heard in Ciudad Guzman and Colima, while the above the crater were produced by Vulcanian eruptions. In ash column that was 3 km to 4 km high moved to the east September 2005, pyroclastic flows were remobilized as and south of the volcano [Breton et al. 2002]. Ballistics lahars, which reached the power lines in Montegrande. The reached between 3.5 km and 4 km on the north and explosions decreased in 2006, although vapour emissions northeast, which formed impact craters that were more than and small ash columns were still produced [G. Reyes, 2 m in diameter. The activity continued, and on May 10, personal communication]. 1999, another explosion was heard in Colima, which formed Since February 2007, a new dome has started to grow, an ash column 6.5 km high and pyroclastic flows down La and this now exceeds the crater rim. Dome growth still Lumbre and El Cordoban, and produced ballistics up to 4.5 continues, with small emissions [http://www.colima- km away that caused fires on the upper parts of CV. On July estado.gob.mx/seguridad]. Given the recurrence interval of 17, 1999, after 13 hours of seismicity, an eruption formed a Plinian events and the similarities between the present 10-km-high ash plume that produced ash-fall on Zapotitlan activity and the activity that preceded the 1818 and 1913 de Vadillo, 21 km west of CV; block and ash flows ran down eruptions, it has become necessary to evaluate the the ravines 3.3 km towards the south and southwest, which distribution, thickness and effects that the ash would have in buried the vegetation and covered the 1998 lava flow the future. [Saucedo et al. 2002, Macias et al. 2006]. The explosion produced a crater with a diameter of 230 m and a depth of 5. Wind distribution 70 m to 80 m. On July 18, 1999, the pyroclastic flows were The dispersion of volcanic ash is controlled mainly by remobilized as hot lahars, which followed the same south- wind transport, and meteorological data of wind direction southwest path [Breton et al. 2002]. Small explosions and low and speed have been used to identify the patterns of tephra seismicity continued for several months [Breton et al. 2002]. dispersal at Etna [Andronico et al. 2005], Popocatepetl During 2000, lava flowed down the Beltran, Durazno [Delgado 2001, Martin Del Pozzo et al. 2008], CV [Navarro and Cafecito ravines on the southeast side of the volcano, et al. 2003], Auckland Volcanic Field [Houghton et al. 2006] with accompanying Merapi flows. During the rainy season, and Nevado de Toluca [Aceves et al. 2007], among others. these were remobilized as lahars, and they damaged the In the present study, we proposed a detailed wind study bridge over the state highway, which isolated the per month because Plinian eruption plumes can encounter communities of San Jose del Carmen and La Becerrera large variations in horizontal wind speeds. At CV, the vertical [http://www.ucol.mx]. In 2001, another eruption produced wind distribution was divided in four altitudinal levels that block and ash flows towards the southwest, and ash-fall on were based on wind direction and speed. The wind data was San Marcos and , as well as new impact craters to the grouped as January to March, June to August, and November north of CV [GVN 2001]. During May 2001, the formation and December, because of similar directions, and data from of a new dome was reported, and a spine on the dome was April, May, September and October were included. observed in December 2001 [GVN 2001]. In January 2002, The dominant wind direction at level I (4,000-9,000 m the dome growth continued. In February 2002, lava flowed a.s.l.) is westerly-south-westerly from January to May and southwards, followed by pyroclastic flows [Smithsonian from November to December. At this level, from June to Institution 2000]. From March to May 2002, there was September, easterly winds prevail, while during October, the frequent sliding from the front of the lava flows, so the trade winds are very unstable, so the wind can blow in any authorities evacuated several towns to the southwest and direction, with a maximum speed of 100 km/h. Figure 3 southeast of CV from May 18 to June 3, 2002. Lava shows the wind directions for each level according to the extrusion continued until February 2003, and in July and month of the year. August 2003, eruptions produced block and ash flows and 3- At level II (9,000-14,000 m a.s.l.), the dominant wind km-high ash plumes that travelled to the southwest and direction is westerly-south-westerly from January to March northwest, and ash fell on the town of at ~60 km and from October to December. In April and May, the to the northwest of CV [Smithsonian Institution 2003]. The dominant wind is westerly, while from June to September, eruption was noisy due to rocks tumbling down the slopes. the wind direction is variable. At level II, the greatest wind There were several small ash emissions until December velocity is 150 km/h from January to May, and 100 km/h 2003, when an eruption produced ash-fall in Ciudad from June to December.

56 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Figure 3. Monthly wind directions for altitudinal levels, based on radiosonde data (1990-2005) from the Manzanillo Station. Wind direction frequency diagrams showing average percentage of time that winds blow towards sectors centered on 4 sectors.

The winds at level III (14,000-17,000 m a.s.l.) are similar [Saucedo et al. 2010]. Here we have thus integrated the wind to those at level II: the dominant winds are west-south- distribution at level IV (from 17,000-28,000 m a.s.l.) and westerly from January to May and from October to estimated the ash dispersion for a similar event to that of December, while there are easterly winds with secondary 1913. The dominant wind course, as the greatest frequency directions from June to September. At this level, the per month, for level IV was used to establish the scenarios maximum wind speed is more than 150 km/h from January that would result from a Plinian eruption. to May and in November and December, and 100 km/h from June to October. 6. Ash-fall scenarios At level IV (17,000-28,000 m a.s.l.), the wind data was Many theoretical and experimental models have been divided into six groups according to similar wind directions developed from the buoyant plume theory, as modified for in several months: January to March; April and October; volcanic eruptions [Wilson et al. 1978, Carey and Sparks May; June to August; September; and November and 1986]. Similarly, many studies have applied semi-analytical December. At this level, south-westerly winds prevail from and numerical models for the transport and deposition of January to March, and westerly in April and October. During volcanic ash based on vulcanological parameters, such as: May, south-south-westerly and south-south-easterly winds total mass, column height, column shape coefficient, grain dominate, from June to August, south-easterly winds prevail, size, mass eruption rate, and daily wind profile per season while in September and in November and December, the [Folch and Felpeto 2005, Macedonio et al. 2008, Costa et al. easterly winds fluctuate. The maximum wind speed is 150 2009, Selva et al. 2010]. These studies have proposed hazard km/h from January to March and in November and maps for ash-fall at Vesuvius and Campi Flegrei. The 1913 December, with 100 km/h from April to August, and 50 CV eruption was shorter than the 1979 Vesuvius eruption, km/h in September and October. This level is associated although the column height and mass was similar (Table 3). with the very fast winds (the jet stream). The scenario constructions for CV are here based on ash-fall In a Plinian eruption, ash plumes can reach the depths, and take into account the isopach thickness from the stratosphere (between 16 km and 30 km high), which would 1913 Plinian eruption (Table 4), the dominant wind direction, allow for higher and wider ash dispersion. The Plinian the total number of people, and the main economic column height in the 1913 eruption was estimated at 23 km activities, land use and communications infrastructures.

57 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Table 3. Main parameters! of the 1913 eruption as compared to other Plinian eruptions.

Scenario 1 which is 5.3 km from the CV crater, and the radio and From January to March, the dominant wind direction is television microwave station on the northern flank of the towards the northeast (Figure 4). Nevado Volcano would be destroyed.

100 cm 15 cm More than 100 cm of tephra would cover areas up to a With 15 cm to 50 cm of ash, lapilli and pumice fall, areas distance of 3 km (Figure 4). The Playon area on the northern northeast of CV, between 11 km and 38 km from the CV part of CV and the north-eastern slope of the Nevado de crater would be affected (Table 5). In this area, there are Colima would be covered by ash and pumice. Mature pines more than 100,000 inhabitants who would be subject to would survive, as occurred in 1913, although their branches stress and corneal abrasion, as well as irritation of the eyes, would break off due to the weight of the ash, and the small skin, nose, scalp and respiratory system, due to the ash pine trees and holm oaks in the area would be buried. Many [Horwell and Baxter 2006, Nieto et al. 2007]. Agriculture, wild animals, such as pumas, mountain cats, ocelots and cattle ranching, and trade and tourism would be affected deer, and many types of birds, like hawks and humming (Table 5). The ash-fall would bury crops and cause birds, all of which are endangered species, would die. The defoliation of fruit trees, which would result in seasonal crop thick ash-fall would also kill insects and reptiles. Ash abrasion loss and a higher percentage of deformed fruit. Livestock on the insect epicuticular wax layer causes rapid desiccation would get sick and/or die after consuming contaminated and death [Cook et al. 1981]. Fires caused by ballistics would grass and water. It would be difficult for the animals to find burn off the vegetation. The seismic station to the north of food and water sources. In the 1818 and 1913 eruptions of the crater would be destroyed. CV, ash also caused roof collapses, while in Ciudad Guzman, several cows died after drinking polluted water and eating 50 cm on pastures with ash [Waitz 1932]. From 50 cm to 100 cm of ash would be expected The Juan Barragan and Ejido Atenquique springs supply between 3 km and 11 km from the crater on the north- drinking water to local people. Water ducts and pumps eastern quadrant of the Nevado de Colima National Park. would be affected by ash abrasion, and the system would get This zone is covered by coniferous forests with natural blocked or destroyed, as happened in Ciudad Guzman in the grasslands, and it is a popular camping site. The ash would 1913 eruption. There are radio and television microwave bury small trees and grass, and break off tree branches. The stations on the north-eastern flank of CV, power substations wild animals, and especially birds, would die. The seismic in Ciudad Guzman, and power lines that supply electricity and visual monitoring equipment at the Nevado Volcano, to the Guadalajara metropolitan area. The ash would cause transmission problems, due to interference and cable and plate abrasion. The alarm system for lahars in Juan Barragan and Atenquique would be damaged too. The unpaved roads that lead to Juan Barragan and Ejido Atenquique would be blocked by ash and fallen trees, and the main roads (Colima-Guadalajara) would also be paralyzed due to blockage, lack of visibility, and damage to the oil, fuel and air filters of vehicles. This would limit the effective response of the emergency services. The 1770, 1818 and 1913 eruptions caused darkness in the area, and in the May 18, 1980, eruption of Mount St. Helens, many thousands of kilometers of country roads, municipal streets and irrigation ! Table 4. Depth ranges of the ash-fall of the 1913 Plinian eruption. district service roads were closed for weeks [Schuster 1982].

58 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Figure 4. Scenario 1. For an eruption from January to March, showing the northeast area that would be affected by a future Plinian eruption. Two scales shown according to isopach contours: top, >1 cm; bottom, 0.01 cm to 0.5 cm. The maps show the main cities, populations and airports. Towns: (Pl) El Platanar; (Bo) El Borbollon; (Be) La Becerrera; (JB) Juan Barragan; (Ag) El Agosto; (Ma) San Marcos; (Te) El Tecuan; (At) Atenquique; (EA) Ejido Atenquique; (Mz) Los Mazos; (Ca) Las Canoas; (MF) La Mesa y el Fresnito; (Al) Alcaraces; (ZV) Zapotitlán de Vadillo; (Dto) El Destacamento; (PE) Los Pozos y el Ocote; (VH) Vista Hermosa; (SJG) San José de Gracia; (LB) Loma Blanca; (AE) Agua Escondida; (EC) El Carpintero; (Ayn) Atequizayán; (US) Usmajac. Inset: wind diagram showing frequency in percentage and wind speed in km/h.

59 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Table 5. Scenario! 1. Localities, populations, main economic activities and roads which would be affected by different ash-fall levels during an eruption occurring from January to March.

The Zapotlan Lagoon is located 30 km northeast of CV. lack of visibility and ash accumulation, which would produce This is a wetland of international importance, where the traffic jams for hours, or even for several days. The power aquatic plants, migratory birds, insects and fish would be at stations in Sayula and Tamazula supply electricity to the risk. The ash would cause changes in the water pH and a region. Lightning and ash abrasion would damage the fuses decreasing food supply; some fish are very susceptible to in substations and would cause power shortages and water changes and would die or get scale disease. blackouts.

>1 cm 0.5 cm From 1 cm to 15 cm of ash would be expected between From 0.5 cm to 1 cm of ash-fall would be expected 38 km and 64 km from CV. There are 70,000 people who live between 64 km and 160 km from CV. This area includes the in this area. The ash would cause eye, skin and nasal more than 4 million people who live in the metropolitan area irritation, and respiratory problems. Farming and cattle of Guadalajara and in small towns (Table 5). The effects in ranching would also be affected. Crops would be destroyed the future would be greater than in 1913 because of the by being buried, and even more mature plants would suffer higher population density. The roofs would have to be severely from the ash. Cattle would get sick or die through cleaned due to ash, and economic activities would be affected ingestion of contaminated pastures and water. Ash-fall temporarily by lack of services and road access (Table 5). would damage chimneys and roofs of the sugar mill in Corn and vegetable crops in the early stages of growth Queseria and the paper mill in Atenquique. would be damaged by the ash, and livestock would get sick The Colima-Guadalajara and Tuxpan- by eating pasture with ash. highways have constant traffic, which would be affected by Guadalajara is the second largest city in Mexico and has

60 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO one of the busiest international airports, which handles would be incorporated into the soil in days, or even be 136,000 flights/year. The ash cloud would force the airport carried away by the wind (Table 5). to close operations for hours or days, and would result in the The thermoelectric power stations in Salamanca and deviation of air routes. The ash accumulation on airport San Luis Potosi are important sources of income, as are the runways, taxiways and aprons would need to be cleaned. In petrochemical and refinery industries in Salamanca. The ash 1990, the ash from the Redoubt Volcano (Alaska) remained would increase the pollution in the environment and cause in the atmosphere and in the flight paths of many skin and eye irritation as well as respiratory problems in the aeroplanes, which caused the Anchorage Kenai Airport, population. located 80 km from the volcano, to remain closed for several The airports in Aguascalientes, San Luis Potosí and days [Casadevall 1994]. Ciudad Victoria handle between 11,506 and 23,071 The main highways in the Colima area connect international flights/year, while the airport in Celaya has important cities, such as Guadalajara, Manzanillo, Ciudad 2,400 national flights/year. Fine ash would lead to flight Guzman, León, Morelia and Mexico City. The lack of cancellations due to ash in the air. The effects on the visibility due to ash-fall would cause problems with traffic. Panamerican highway and the power stations in San Luis The power stations in Guadalajara and Atotonilco supply Potosi and Saltillo would be minimal. electricity to over one million users. The towers and cables would be damaged by ash, causing power shortages and Scenario 2 blackouts or power interruptions to homes, industries, shops The wind direction in April and October is eastwards and administrative services for hours or days. The alarm (Figure 5). The area that would be affected is similar to that system for lahars in San Marcos would be damaged. of the 1818 eruption, when ash fell in Ciudad Guzman, Chapala is the largest lake in Mexico, and it is a habitat Guadalajara, , Leon, Guanajuato, for several species of migratory birds, such as the white Zacatecas, San Luis Potosi, Querétaro and Mexico City pelican, as well as native plants and animals. This region has [Arreola 1915, Waitz 1932]. conservation programs to maintain the natural habitats of the lake, but ash-fall would produce serious contamination 100 cm of the lake and modify the pH and nutrient conditions. Ash- The coniferous forest (Mexican fir oyamel, cedar and fall would also hinder the flight of birds. pine) on the eastern flank of the Nevado de Colima would be covered by more than 100 cm of ash, lapilli and pumice, as in 0.1 cm scenario 1, and similar effects could be expected. Some mature From 0.1 cm to 0.5 cm of ash would be expected trees could survive, but the small trees would be buried. Some between 160 km and 390 km from the CV crater. In this area, animals would die due to asphyxia or desiccation. The fires there are more than 1 million inhabitants. There would be caused by ballistics would burn off the vegetation. respiratory problems because of the ash, although the effects on industry and trade would be minimal. The ash would 50 cm have positive effects on some agricultural areas, because In the areas where 50 cm to 100 cm of ash would fall, small amounts can act as natural fertilizers, but with cattle it the distribution would be similar to the 50 cm isopach in would cause diarrhea and weight loss, and reduced meat and scenario 1. The area is covered by coniferous forests with milk production [Fonseca et al. 2007]. natural grasslands, which would be buried by ash, and the The city of Leon has an international airport with wildlife would die. 27,206 flights/year. The ash would force the airport to interrupt operations for hours due to ash in the air routes. 15 cm In this area, the Panamerican highway that connects México From 15 cm to 50 cm of ash, lapilli and pumice would City, Morelia, Querétaro, Irapuato and León would be affect eastern areas between 11 km and 38 km from the CV affected. The main problem with the ash would be the traffic crater. Over 20,000 people live in this area, mainly in small towards Guadalajara. The power stations in Leon and in communities (Table 6). Effects similar to those of scenario 1 Zamora would suffer damage to the transformers, which (15 cm) would expected. The ash would also cause roof would cause blackouts. collapses. The vegetables and agave crops would be buried (Table 6). Livestock would get sick and/or die, and it would 0.01 cm cause a decline in meat, egg and milk production. With 0.01 cm to 0.1 cm of ash-fall, this would reach The Atenquique paper mill would be affected between 390 km and 725 km from CV. In this area, there are significantly by ash-fall, causing a decrease in the production more than 2 million inhabitants. The ash would have of cellulose. Raw materials stored out in the open, as well as minimal effects on the economy of the area, because it the chimneys and roofs, would be damaged by ash-fall.

61 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Figure 5. Scenario 2. For an eruption in April or October, showing the eastern area that would be affected by a future Plinian eruption. For details, see legend to Figure 4.

62 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Table 6. Scenario! 2. Localities, populations, main economic activities and roads which would be affected by different ash-fall levels during an eruption occurring from April and October.

Furthermore, silting of the river would be a threat in the railroads would be blocked by ash. rainy season, with the possible formation of lahars, and the The radio and television microwave stations on the alarm system for lahars in Juan Barragan, Atenquique and northeast part of CV and in Tuxpan would have San Marcos would be damaged. transmission problems due to interference and plate The main Guadalajara-Manzanillo highway connects abrasion. Sayula, Tuxpan and Zapotiltic each have a power western Mexico with the Pacific coast. The railroad line station, and power lines from Manzanillo supply power to links the center of Mexico with the port of Manzanillo, and Guadalajara; the ash would cause failures in electrical transports import and export goods. The roads and supplies and disruption of services.

63 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

>1.0 cm quality and ecology. During the 1980 Saint Helens eruption, From 1 cm to 15 cm of ash would be expected between the volcanic ash-leachates that fell in Richland Lake were 38 km and 64 km from the CV crater. More than 130,000 toxic for the algal populations [McKnight et al. 1982]. people live in this area. The effects on the people and economic activities would be similar to scenario 1 with more 0.01 cm than 1 cm of ash. The forage grass would be buried, and the From 0.01 cm to 0.1 cm of ash-fall would be expected up cattle would get sick or die by eating contaminated pasture. to 725 km from CV. In this area, more the 25,000,000 people Ash-fall would also damage chimneys and roofs of the sugar live in Querétaro, Mexico City, Toluca, Puebla, Cuernavaca, mill in Queseria. Pachuca, Tula, Poza Rica and many small towns. The small The national airport in the city of Colima (5,207 amounts of ash would have minimal effects on crops, flights/year) would cancel services due to the ash in the air because it would be incorporated into the soil in days or routes and airways. The Federal highway and roads that link weeks, and even be carried away by the wind. Colima, Ciudad Guzman, Tamazula and the surrounding In Salamanca, the petrochemical industry and refinery towns would be blocked for hours or days. The ash on the are important sources of income, as well as the power stations in Ciudad Guzman and in Tamazula would thermoelectric power stations (including the one north of cause short circuiting and blackouts. Mexico City). The ash in the atmosphere would increase the pollution in the environment and would cause respiratory 0.5cm problems for the people. From 0.5 cm to 1 cm of ash fall would affect areas east Fine ash would affect the international airports of of CV, between 64 km and 160 km from the crater. There are Mexico City (355,593 flights/year) and Puebla (17,277 more than 700,000 people living in this area, who would be flights/year), Querétaro (12,733 flights/year), Toluca subject to similar effects as in scenario 1 with a 0.5 cm of ash. (unspecified flights) and Cuernavaca (unspecified flights), as The tomato, bean and oat crops would be damaged, and the well as the national airports in Celaya (2,400 flights/year) and livestock would get sick because of the ash. Pachuca (3,707 flights/year), and cause deviation of air The area has national airports in Zamora (1,061 routes and interrupt operations for hours. The effects on the flights/year) and Uruapan (6,010 flights/year), so the ash main highways and secondary roads would be small. would force these airports to close and the airways would need to be cleaned. The two main highways between Scenario 3 Guadalajara and Colima and Morelia and Lazaro Cardenas In May the dominant wind blows to the north-northeast link the Pacific with central Mexico. These roads would be and north-northwest, which results in two possible scenarios. closed because of low visibility and ash accumulation. The Scenario 3 towards the north-northeast (Figure 6) would power stations in Colima, Sahuayo, Sayula, Uruapan and be similar to the 1913 eruption, when tephra fell on San Zamora supply electricity to the region, and the ash would Marcos, Tonila, Queseria, Ciudad Guzman, Zapotiltic, Tuxpan, damage the transformers and cause blackouts. Sayula, Guadalajara, Aguascalientes, Fresnillo, Zacatecas and Saltillo, and on small towns and farms [Waitz 1932]. 0.1 cm From 0.1 cm to 0.5 cm of ash would be expected 100 cm between 160 km and 390 km from CV, where more than More than 100 cm of ash would be expected in the first 900,000 people are living in the city of Morelia and in small 3 km on the north-north-eastern flank of CV. This area is towns. The impact on the people and the economic activities covered by coniferous forest and alpine vegetation that would be similar to scenario 1 with 0.1 cm of ash. The ash would be buried, and the fauna would die. Ballistics would would have positive effects on some agricultural areas, but cause fires and burn the vegetation. The effects would be the the cattle would get sick, with reductions in meat and milk same as in scenario 1 with 100 cm of ash. production. Fine ash in the atmosphere would force the 50 cm international airport in Morelia (18,144 flights/year) to shut From 50 cm to 100 cm of ash would affect the south- down for days. The Lázaro Cárdenas-Morelia-México south-eastern portion of Nevado de Colima, between 3 km highways connect western Mexico and central Mexico, and and 11 km from the CV crater. The coniferous forests and the lack of visibility caused by the ash would create traffic grasslands would be buried in ash. Small mammals, birds, problems. insects and reptiles would die. The seismic and visual The Cuitzeo and Patzcuaro lakes are habitats with monitoring equipment and the radio and television endangered species, such as the white fish and Canadian microwave station on the northern flank of Nevado de duck. The ash would have adverse effects on the lake-water Colima would be destroyed.

64 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Figure 6. Scenario 3. For an eruption in May, showing the first potential, north-northeast, area that would be affected by a future Plinian eruption. For details, see legend to Figure 4.

65 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Table 7. Scenario! 3. Localities, populations, main economic activities and roads which would be affected by different ash-fall levels during an eruption occurring in May (north-northeast level IV winds).

15 cm paralyze production. Ash-fall and lightning would damage the From 15 cm to 50 cm of ash-fall would affect areas alarm systems for lahars in Juan Barragan and Atenquique. between 11 km and 38 km from CV, where more than The main roads in this area are the Guadalajara-Ciudad 120,000 people live (Table 7). These people would suffer from Guzmán and Guadalajara-Colima highways, as well as the stress, skin and eye irritation, and respiratory problems. The secondary roads that connect the towns near CV. The effects on crops and livestock would be similar to scenario 1 accumulation of ash would immediately paralyze with 15 cm of ash. transportation in the area. The Tolteca cement plant is a producer of lime, cement and marble, and it is located in Zapotiltic. The economic >1.0 cm impact on this area would be significant, because of chimney From 1 cm to 15 cm of ash would be expected between obstruction and machinery damage in factories, which could 38 km and 64 km from CV. More than 70,000 people live in

66 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO this area. The impact expected on people would be similar to Furthermore, the international airport in Aguascalientes previous scenarios with >1.0 cm of ash. Orchards, sugar cane would interrupt operations for hours due to the ash in the and corn, as well as forage grass in the early stages of atmosphere. growth, would be buried, and more mature plants would even suffer severely from the ash; the cattle would get sick. 0.01 cm The sugar mill in Queseria, the cement factories in From 0.01 cm to 0.1 cm of ash would be expected up to Zapotiltic, and the paper mill in Atenquique would be 725 km from CV. There are more than 3 million inhabitants affected. Raw materials stored out in the open and the in this area, in Leon, San Luis Potosí, Zacatecas, Guanajuato chimneys and roofs would be damaged. and Saltillo, and in small towns. The effects would be similar The Colima-Guadalajara-Tuxpan highways have to scenario 1 with 0.01 cm of ash. constant traffic and would be closed due to the lack of The power stations in San Luis Potosi and Saltillo, and visibility and accumulation of ash. The power stations in the main roads like the Panamerican highway, would suffer Tuxpan and Sayula supply electricity to 43,936 users, and minimal effects. This scenario includes the international here the ash-fall would cause short circuits in transmission airports of Leon (27,206 flights/year), San Luis Potosi lines. Lightning would interrupt radio and television (24,430 flights/year), Zacatecas (8,257 flights/year) and transmission at the microwave station in Tuxpan, and Saltillo (13,165 flights/year), and the national airport in damage the alarms for lahars in San Marcos. Zamora (1,061 flights/year). Fine ash would lead to flight cancellations, due to the fine ash in the air. 0.5 cm From 0.5 cm to 1 cm of ash-fall would be expected Scenario 4 between 64 km and 160 km from the CV crater, where there In May, the winds also blow north-north-westerly, are more than 4,580,000 people. The ash would cause similar resulting in this second May scenario (Figure 7). effects as in previous scenarios with 0.5 cm of ash. The economic activities would be affected temporarily by the lack 100 cm of services and road access. More than 100 cm of tephra would be expected 3 km The highways that connect important cities, such as from the CV crater, on the north-north-western flank of CV. Colima, Guadalajara, Manzanillo, Ciudad Guzman, León, The coniferous forest would be covered by ash and pumice, Morelia and Mexico City, would be affected by a lack of and wild animals would be buried, as in previous scenarios visibility, and ash accumulation would cause traffic problems. with 100 cm of ash. With the power stations in Guadalajara, Sahuayo, Ocotlan, Tamazula and Poncitlan, which supply electricity to more 50 cm 600,000 users, the ash would cause power shortages and From 50 cm to 100 cm of ash would be expected blackouts. The international airport in Guadalajara would between 3 km and 11 km from the CV crater on the south- be forced to close operations for hours or days. south-western sector of the Nevado de Colima (Table 8). Lake Chapala would also be affected by ash deposition, This zone is covered by coniferous forests and grasslands, and the effects would be similar to scenario 1 with 0.5 cm where wild animals live, such as small mammals, and many of ash. types of birds, insects and reptiles. The impact expected on the vegetation and fauna would be similar to that in 0.1 cm previous scenarios with 50 cm of ash. The ash, pumice and From 0.1 cm to 0.5 cm of ash would be expected lapilli would also damage the microwave station on the between 160 km and 390 km north-northeast from the CV northern flank of Nevado Volcano and the seismic and crater. There are more than 900,000 inhabitants in this area, visual monitoring equipment at Nevado, 5.3 km from the and the ash would cause skin, eye and respiratory problems. CV crater. This is one of the main milk-producing areas in the country, which supplies the markets of Guadalajara, Aguascalientes 15 cm and Mexico City. The impact on economic activities would From 15 cm to 50 cm of ash would fall between 11 km be similar to those in scenario 1 with 0.1 cm of ash. and 38 km to the north-northwest of CV. More than 4,210 The Panamerican, Barra de Navidad-Tampico and people live in this area, who would be subject to stress, and Guadalajara highways connect with Morelia, Querétaro, eye, skin and respiratory problems. Ash-fall would bury México City and Aguascalientes. The lack of visibility due to crops (tomatoes and potatoes) and cause roofs of the ash would cause traffic jams. The power stations in greenhouses to collapse. Livestock would get sick or die after Aguascalientes and Lagos de Moreno supply electricity to consuming contaminated pasture and water. San Gabriel has more than 300,000 users, and there would be blackouts. a power station and a radio and television microwave station,

67 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Figure 7. Scenario 4. For an eruption in May, showing the second potential, north-northwest, area that would be affected by a future Plinian eruption. For details, see legend to Figure 4.

68 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

! Table 8. Scenario 4. Localities, populations, main economic activities and roads which would be affected by different ash-fall levels during an eruption occurring in May (north-northwest level IV winds). where the transformers and towers would be damaged by economic activities would be similar to scenario 1 with more lightning during the eruption, which would cause shortages than 1 cm of ash. The cement factories in Zapotiltic would and lack of electricity. The Guadalajara-San Gabriel highway be affected. would be closed. Power stations in San Gabriel, Sayula, Ciudad Guzman, Gomez Farias, Tuxpan and Zapotiltic supply electricity to >1 cm more 70,000 users. The ash and lightning would cause short From 1 cm to 15 cm would be expected between 38 km circuits in transmission lines. The radio and television and 64 km north-northwest of the CV crater, where 150,000 microwave stations in Sayula, Tuxpan and Ciudad Guzman people live in many towns. The effects on the people and would suffer transmission problems due to ash interference.

69 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Main highways, such as the Guadalajara-Manzanillo and forced to interrupt operations for hours or cause deviations Guadalajara-Sayula highways (and the Guadalajara-Nogales to their air routes. railroad) that link the Pacific Coast to north-central Mexico would have traffic jams towards Guadalajara or the Pacific Scenario 5 due to ash on the roads. From June to August, there is a high probability that the The pH and nutrient conditions in the Zapotlan and winds would blow towards the northwest (Figure 8). Sayula Lagoons would be modified by ash silting, and the native plants and animals would die. 100 cm More than 100 cm of tephra would be expected 3 km 0.5 cm from the CV crater on the north-western flank of CV. This From 0.5 cm to 1 cm could be expected between 64 km area is also covered by coniferous forests and grassland that and 160 km from CV, where around 4,332,049 people live; would be buried by ash, pumice and lapilli. Birds, insects and the impact of the ash would be the same as scenario 1 with reptiles would die, as in previous scenarios with 100 cm of a 0.5 cm thickness. The economy would be affected ash. temporarily by the lack of services and road access. The Guadalajara international airport would have to 50 cm close operations for hours or days due to ash clouds and ash From 50 cm to 100 cm of ash would be expected over the airstrips. The power stations in Guadalajara, between 3 km and 11 km from CV, on the north-western side Cuquio, El Grullo, Mazamitla, Unión de Tula and Valle de of CV. The coniferous forest and grass would be buried by Juarez supply electricity to over one million users, and the ash, pumice and lapilli, and fires would burn the vegetation. ash would cause power shortages and blackouts. The The local fauna of this zone would die. microwave stations in Guadalajara, El Grullo and Mazamitla would have interference problems. Main roads, such as the 15 cm Guadalajara-Manzanillo and Guadalajara-Saltillo ones, From 15 cm to 50 cm of ash could affect areas between would have traffic problems due to lack of visibility. 11 km and 38 km from the CV crater, where more than 9,150 Lake Chapala would also have serious pollution due to inhabitants live (Table 9). The immediate effects on the the ash, as in scenario 1 with 0.5 thickness. population would be stress, and skin, eye and respiratory problems, with an impact on trade, farming, ranching and 0.1 cm industry, similar to scenario 4 with 15 cm of ash. From 0.1 cm to 0.5 cm of ash would be expected The Guadalajara-Ciudad Guzmán and Guadalajara-San between 160 km and 390 km north-northwest from CV. The Gabriel roads would be forced to close temporarily to socioeconomic effects over the Sierra Huicholes area would remove the ash. Furthermore, the microwave stations in San be minimal due to the lower population density. Gabriel and on the northern flank of CV would have interference problems during ash-fall. San Gabriel has a 0.01 cm power station and the transformers would be damaged by From 0.01 cm to 0.1 cm of ash would be expected up to lightning, which would cause a lack of electric power for 725 km to the north-northwest of CV. More than 1,303,876 several days. Zapotitlan de Vadillo has a runway for people live in this area, in Tepic, Fresnillo, Durango and aeroplanes, which would be obstructed by ash accumulation. Zacatecas. The fine ash would cause effects similar to those in scenario 1 with 0.01 cm of ash. >1 cm Tepic has two refineries that represent major sources of From 1 cm to 15 cm of ash would be expected between employment for local households throughout the state. The 38 km and 64 km northwest of CV. Around 30,123 people hydroelectric plants in Tepic and Durango, with capacity live in this area, who would have problems as in previous from 320 megawatts to 960 megawatts, are the most scenarios with >1 cm of ash. The Borbollon, Schulte and El important power production facilities in the area. The ash in Jabali ranches are private environmental protection areas the atmosphere would increase the pollution in this area. that have sustainable management of natural resources. The Mazatlán highway that connects México City with Likewise, the Hacienda San Antonio, a luxury hotel, and the north-western Mexico would see small effects. The power La Maria Lake cabins employ local people. Furthermore, and microwave stations in Tepic, Fresnillo, Durango and mountain biking and picnicking are important week-end Zacatecas would have interference due to the ash. There activities around the CV and the Nevado de Colima, which are international airports in Zacatecas (8,257 flights/year) would be closed for several months. and Durango (15,676 flights/year), as well as a national Zapotiltic and Atenquique would experience increased airport in Tepic (10,837 flights/year), which would be aerosol contents in the atmosphere, and the machinery and

70 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Figure 8. Scenario 5. For an eruption from June to August, showing the northwest area that would be affected by a future Plinian eruption. For details, see legend to Figure 4.

71 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Table 9. Scenario! 5. Localities, populations, main economic activities and roads which would be affected by different ash-fall levels during an eruption occurring from June to August. chimneys of the paper and cement industries would be 0.5 cm damaged by ash abrasion. Silting of the Zarco and La From 0.5 cm to 1 cm of ash would be expected between Lumbre rivers due to accumulation of pyroclastic material 64 km and 160 km to the northwest of the volcano, where would trigger the formation of lahars during the summer. there are more than 87,777 people. The expected impact on The Lumbre and Zarco bridges would be damaged, thus people, trade, farming and cattle ranching would be similar blocking the San José del Cármen-Suchitlán road. to scenario 1 with 0.5 cm of ash. The sector to the west of CV has a network of roads, such The Guadalajara-Manzanillo, Guadalajara-Barra de as the Manzanillo-Colima, the Comala-San José del Cármen- Navidad and El Grullo-Ciudad Guzmán highways would Zapotitlán de Vadillo, and the Carrizalillos-Quesería highways, have poor visibility and would experience traffic problems. which would be blocked by ash accumulation. Power stations The radio and television stations in El Grullo and Mazamitla in Zapotiltic supply electricity to more 10,247 users. The ash would have interference problems. In this area, the power and lightning would cause short circuits in distribution lines. stations in Cuquio, El Grullo, Unión de Tula and Valle de The microwave station in la Becerrera would also have Juarez supply electricity to countless users. The ash would transmission problems due to interference or ash abrasion. cause power shortages and blackouts.

72 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

In the Zapotlán and Sayula Lagoons, the ash-fall would 100 cm produce contamination by silting and modification of the More than 100 cm would fall up to 3 km from the CV conditions of pH and nutrients. crater, on the western flank of CV. This area is also covered by coniferous forests that are associated with natural grasslands. 0.1 cm The ash would bury the vegetation and the wild animals, and From 0.1 cm to 0.5 cm of ash would be expected especially the birds, insects and reptiles would die. between 160 km and 390 km on the north-western side of CV. This area has 689,833 inhabitants, in Tepic, the Puerto 50 cm Vallarta metropolitan area, and many towns. Puerto Vallarta From 50 cm to 100 cm of ash would be expected the third largest port in Mexico, and it receives more than 5 between 3 km and 11 km on the western side of CV. The ash- million tourists each year. The economy of the area depends fall would bury the coniferous forests and natural grasslands. on tourism, which accounts for roughly 50% of all of the The wildlife would die, as in previous scenarios with 50 cm economic activity in the Puerto Vallarta metropolitan area. of ash. The impact would become significant for private The manufacturing industry and refineries in Tepic, and the areas, such as the El Jabali, Shulte and El Borbollon ranches hydroelectric plants in Aguamilpa and Jumatan are the chief in the southwest, because they would be destroyed. The income sources for the local population. Other important coffee, corn and agave crops, and orchards and livestock sources are trade, farming and cattle ranching. Tourism would be covered by the ash. during the summer would be paralyzed for hours or days due to ash-fall. 15 cm The Pacific highway and the Guadalajara-Vallarta, Tepic- From 15 cm to 50 cm of ash-fall would affect areas west Mazatlan freeways would have traffic problems. Puerto of CV. In this area, there are more than 5,738 inhabitants, Vallarta also has a maritime infrastructure that provides who would suffer eye, skin and respiratory problems, as well services to cruise ships and private boats, and provides local as nervousness, as for the previously described scenarios with tourist transportation. The microwave stations in Tepic and 15 cm thickness (Table 10). The ash would cover the crops Puerto Vallarta would have interference of the radio and and the cattle would die or have gastrointestinal diseases after television signals, and the ash would paralyze these activities eating contaminated grass. for hours or days. The international airports in Puerto The Zapotitlán de Vadillo-Guadalajara road would be Vallarta (38,892 flights/year) and Tepic (10,837 flights/year) closed, and it would be necessary to remove the ash. The would be forced to interrupt flights for hours, and would radio and television microwave station in La Becerrera would require clean-up operations on the runways and aircraft. be damaged during the ash-fall. The runways for aeroplanes in Zapotitlan Vadillo and at the Jabali ranch would be 0.01 cm obstructed by ash accumulation. From 0.01 cm to 0.1 cm of ash would be expected between 390 km and 725 km from CV. In this area, there are > 1 cm more than 699,373 inhabitants, in the Colima metropolitan From 1 cm to 15 cm of ash would be expected between area, and in Mazatlán, Islas Marias and small towns. Mazatlan 38 km and 64 km to the west side of CV, an area that has is one of the most important Mexican ports because of its more than 319,840 inhabitants. The population would international trade and cruise-related tourism from the experience the same impact as in scenario 1 with >1 cm of United States, and it is the main link with the La Paz port in ash. The cereal crops would be damaged during the Baja, California. Furthermore, the Islas Marías are four pollination period, thus reducing grain quality; livestock islands where the Marias Prison is located. Nonetheless the would get sick or die by eating contaminated pasture. impact would be minimal. The state roads connecting Zapotitlán de Vadillo-Colima The power stations in Mazatlan and Colima, as well as and Colima-Puerto Vallarta would be closed due to lack of the Colima-Manzanillo, Guadalajara-Tepic and Mexico- visibility and accumulation of ash. The power stations in Nogales roads, would expect little damage. The airports in Colima supply electricity to 54,939 users, and it would suffer Manzanillo (8,004 flights/year), Mazatlan (no data), Colima blackouts due to short circuits. The microwave station in San (5,207 flights/year), and the private airport in Escuinapa, Gabriel would have transmission problems, and the airport in would be affected by the ash in the atmosphere. Colima would be forced to close operations, to remove the ash from the aeroplanes, runways and taxiways. Scenario 6 In September, the predominant wind direction is 0.5 cm westerly, and ash would be expected to be scattered in the From 0.5 cm to 1 cm of ash would be expected between same direction (Figure 9). 64 km and 160 km to the western side of CV, where there

73 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Figure 9. Scenario 6. For an eruption in September, showing the western area that would be affected by a future Plinian eruption. For details, see legend to Figure 4.

74 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Table 10. Scenarios! 6 and 7. Localities, populations, main economic activities and roads which would be affected by different ash-fall levels during an eruption occurring in September or November and December. are more than 56,208 people living, who would have eye, skin effects on some agricultural areas would be minimal. and respiratory problems. The sugar cane, vegetable and The Colima-Manzanillo highway would have traffic forage grass would be affected. The livestock would get sick problems due to slippery roads and the low visibility caused by eating pasture contaminated with ash. by ash. The international airport in Manzanillo, which The Guadalajara-Manzanillo and El Grullo-Ciudad handles 8,004 flights/year, would suspend operations for Guzman roads would have traffic problems due to a lack of hours or days. In this area, there are also two thermoelectric visibility. The power stations and radio and television plants in Manzanillo, and the ash would increase atmospheric microwave stations in El Grullo and Mazamitla would have pollution there. interference problems. 0.01 cm 0.1 cm From 0.01 cm to 0.1 cm of ash would be expected From 0.1 cm to 0.5 cm of ash would be expected between 390 km and 725 km from CV. In this area, there are between 160 km and 390 km west of CV, an area with more more than 253,996 inhabitants, in Puerto Vallarta, Tecoman than 125,235 people, living in Armeria, Manzanillo, Cuyutlán and Sayula. Ash would also fall in the Pacific Ocean area, and small towns. The population would suffer problems affecting ships. The tourist and maritime activities in this area similar to those in previous scenarios with 0.1 cm of ash. The would also be affected for hours or days. ash would contaminate the salt production in Cuyutlan. The The microwave stations in Puerto Vallarta and in

75 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Tecoman would have few problems, as would the highways 7. Arrival Time of the Pacific area; however, for the airport in Puerto Vallarta It is possible to estimate the time of arrival of the ash that handles 38,892 flights/year, the fine ash would interrupt in the main cities. Ciudad Guzman would expect about 15 flights and airport operations. cm of ash in about 10 minutes if the Plinian eruption occurs from January to May or in October; (Table 12). In Scenario 7 Guadalajara, about 0.5 cm would arrive in less than 1 hour, During November and December, the dominant winds while in León, 0.1 cm would begin falling after nearly 2 blow westward, with slight variations to the west-southwest. hours from January to March and in May. Cities like Mexico Therefore, similar impacts will be expected to those depicted City and Puebla would have ash-fall 5 hours and 6 hours 16 in scenario 6, although the areas affected would be further minutes after of an eruption, if the event occurs in April or south, perhaps producing more ash on Colima and Tecoman in October. Tourist cities such as Manzanillo, Puerto than in September (Figure 10). The scenarios are Vallarta and Mazatlan would expect between 0.1 cm and summarized in Table 11. 0.01 cm of ash 35 minutes, and 2 hours and 4 hours,

Table 11. Cities and! airports which would be affected by future Plinian eruption. P population 1: >1,000,000; 2: 500,000-1,000,000; 3: 100,000-500,000. F number of flights/year (2006), 1: >50,000; 2: 10,000-50,000; 3: 1,000-10,000.

76 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

Figure 10. Scenario 7. For an eruption in November or December, showing the west-southwest area and the Pacific Coast that would be affected by a future Plinian eruption. For details, see legend to Figure 4.

77 PLINAN ERUPTION SCENARIOS: COLIMA VOLCANO

occurring from June to August, the ash would travel towards the northwest, in September, towards the west, and in November and December, towards the west-southwest. The wind directions at the time could fluctuate and modify the scenarios in any secondary directions. The scenarios with a major probability of occurrence are 1 and 2 during January to March, and April and October, as the winds show major stability. The north- eastern and eastern areas are more vulnerable because of the greater density of the populations in those area. The immediate effects on the local population would be respiratory problems and psychological stress. The agricultural and livestock sectors would suffer serious financial losses. Cattle would require supplementary feed, due to contamination of pastures because of the ash-fall. The biggest impact would be on farmer incomes due to the damage the ash would cause to pastures, vehicles and buildings. Likewise, the telecommunications stations on the northern flank of the Nevado Volcano and the seismic and visual monitoring equipment at Nevado, 5.3 km from the CV crater, would be destroyed. The industrial activities of the Queseria sugar mill, the Atenquique paper mill, and the cement plants in Zapotiltic would halt due to the obstruction of their chimneys and the abrasion of any machinery located outside. The Zapotlan Lagoon and Chapala, Cuitzeo and Patzcuaro lakes would have serious contamination by silting and modifications to the conditions of pH and nutrients. The international airports of Guadalajara and Aguascalientes, San Luis Potosí, León, México D.F., and Zacatecas with more 10,000 flights/year, and the national airports of Celaya, Zamora and Colima Uruapan with less ! Table 12. Estimated arrival times for ash in the main cities, according to than 10,000 flights/year might forced to interrupt flights month of eruption and maximum and minimum wind speeds. for hours or days, and would require clean-up operations on the runways and aircraft. The permanently busy respectively, after of the eruption onset, if it is from May to Guadalajara-Manzanillo highway would be blocked by ash December. and lack of visibility. Similar effects would be expected in scenarios 4, 5, 6 and 8. Conclusions 7, with the western areas at risk in the summer, and the Historical analysis has shown that CV has a cyclic tourist and commercial ports of Manzanillo, Puerto Vallarta behaviour, with a VEI 4 Plinian eruption that destroys the and Mazatlán would be affected during high season. The salt central dome occurring approximately every 100 years. The industry in Cuyutlán and the thermoelectric power stations recurrence interval of these Plinian eruptions and similarities in Manzanillo and Tepic would be affected by fine ash. The between the present-day activity and that which preceded airports of Puerto Vallarta, Manzanillo, Mazatlán, Durango, the 1913 eruption indicate that there might be another Colima and Tepic would be forced to close operations. eruption of this type in the near future. Our analysis of wind data from 1990 to 2005 shows that Acknowledgements. The authors would like to thank Don Melchor Urzua, Director of Civil Protection at Colima, and Gabriel Reyes, Head of during a Plinian eruption the ash would be dispersed in the Colima Volcano Observatory, for their kind assistance and different quadrants throughout the year. The scenarios show recommendations while in Colima. The people in the area were always that from January to March, ash-fall hazard zones are situated helpful with the study, and especially Marisela Sandoval. The Universidad to the northeast of CV, in April and October towards the Nacional Autónoma de Mexico funded this study through projects from DGAPA (PAPIIT) and the Instituto de Geofísica. The authors would also east, and in May the areas affected would be mainly to the like to acknowledge the field assistance of their students, Amiel Nieto, north-northeast or north-northwest. In an eruption Mirna Garcia and Dorilen Camacho.

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*Corresponding author: Rita Fonseca, Instituto de Geofisica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacan Mexico D.F., Mexico; email: [email protected].

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